Writing instrument



FIG. 1 is a top, left front perspective view of a writing instrument showing my new design;

FIG. 2 is a front elevational view;

FIG. 3 is a rear elevational view; and,

FIG. 4 is a bottom plan view thereof.

FIGS. 2 through 4 have been drawn to an enlarged scale with respect to FIG. 1. 

The ornamental design for a writing instrument, as shown and described. 